/*
 *    PorterStemmer.java
 *    Copyright (C) 2007 David Milne, d.n.milne@gmail.com
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

package org.wikipedia.miner.util.text;

/**
 * An implementation of the Porter Stemming Algorithm. 
 * This transforms a word into its root form. 
 */
public class PorterStemmer extends TextProcessor {  

	private final Cleaner cleaner ;
	private final Stemmer stemmer ;

	/**
	 * Initializes a newly created PorterStemmer.  
	 */	
	public PorterStemmer() {  
		cleaner = new Cleaner() ;
		stemmer = new Stemmer() ;
	}

	/**
	 * Returns a copy of the argument text, where each term within it is stemmed and cleaned. 
	 * 
	 * @param text	the text to be processed.
	 * @return	the processed version of this text.
	 */
        @Override
	public String processText(String text) {

		String processedText = "" ;
		String[] terms = text.split(" ") ;

		for (String term: terms) {
			if (!"".equals(term)) {
				stemmer.add(term.toCharArray(), term.length()) ;
				stemmer.stem();
				processedText = processedText + " " + cleaner.processText(stemmer.toString()) ;			
			}
		}
		return processedText.trim() ;
	}


	/*

	   Porter stemmer in Java. The original paper is in

	       Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14,
	       no. 3, pp 130-137,

	   See also http://www.tartarus.org/~martin/PorterStemmer

	   History:

	   Release 1

	   Bug 1 (reported by Gonzalo Parra 16/10/99) fixed as marked below.
	   The words 'aed', 'eed', 'oed' leave k at 'a' for step 3, and b[k-1]
	   is then out outside the bounds of b.

	   Release 2

	   Similarly,

	   Bug 2 (reported by Steve Dyrdahl 22/2/00) fixed as marked below.
	   'ion' by itself leaves j = -1 in the test for 'ion' in step 5, and
	   b[j] is then outside the bounds of b.

	   Release 3

	   Considerably revised 4/9/00 in the light of many helpful suggestions
	   from Brian Goetz of Quiotix Corporation (brian@quiotix.com).

	   Release 4

	 */

	/**
	 * Stemmer, implementing the Porter Stemming Algorithm
	 *
	 * The Stemmer class transforms a word into its root form.  The input
	 * word can be provided a character at time (by calling add()), or at once
	 * by calling one of the various stem(something) methods.
	 */
	private class Stemmer
	{  
		private char[] b;
		private int i,     /* offset into b */
		i_end, /* offset to end of stemmed word */
		j, k;
		private static final int INC = 50;
		/* unit of size whereby b is increased */
		
		/**
		 * initializes a new Stemmer
		 */
		public Stemmer()
		{  b = new char[INC];
		i = 0;
		i_end = 0;
		}

		/**
		 * Add a character to the word being stemmed.  When you are finished
		 * adding characters, you can call stem(void) to stem the word.
		 * 
		 * @param ch the character to be added.
		 *//*
		protected void add(char ch)
		{  if (i == b.length)
		{  char[] new_b = new char[i+INC];
		for (int c = 0; c < i; c++) new_b[c] = b[c];
		b = new_b;
		}
		b[i++] = ch;
		}*/


		/** 
		 * Adds wLen characters to the word being stemmed contained in a portion
		 * of a char[] array. This is like repeated calls of add(char ch), but
		 * faster.
		 */
		protected void add(char[] w, int wLen)
		{  if (i+wLen >= b.length)
		{  char[] new_b = new char[i+wLen+INC];
		for (int c = 0; c < i; c++) new_b[c] = b[c];
		b = new_b;
		}
		for (int c = 0; c < wLen; c++) b[i++] = w[c];
		}

		/**
		 * After a word has been stemmed, it can be retrieved by toString(),
		 * or a reference to the internal buffer can be retrieved by getResultBuffer
		 * and getResultLength (which is generally more efficient.)
		 */
		public String toString() { return new String(b,0,i_end); }

		/**
		 * Returns the length of the word resulting from the stemming process.
		 */
		//protected int getResultLength() { return i_end; }

		/**
		 * Returns a reference to a character buffer containing the results of
		 * the stemming process.  You also need to consult getResultLength()
		 * to determine the length of the result.
		 */
		//protected char[] getResultBuffer() { return b; }

		/* cons(i) is true <=> b[i] is a consonant. */

		private final boolean cons(int i)
		{  switch (b[i])
			{  case 'a': case 'e': case 'i': case 'o': case 'u': return false;
			case 'y': return (i==0) ? true : !cons(i-1);
			default: return true;
			}
		}

		/* m() measures the number of consonant sequences between 0 and j. if c is
	      a consonant sequence and v a vowel sequence, and <..> indicates arbitrary
	      presence,

	         <c><v>       gives 0
	         <c>vc<v>     gives 1
	         <c>vcvc<v>   gives 2
	         <c>vcvcvc<v> gives 3
	         ....
		 */

		private final int m()
		{  int n = 0;
		int i = 0;
		while(true)
		{  if (i > j) return n;
		if (! cons(i)) break; i++;
		}
		i++;
		while(true)
		{  while(true)
		{  if (i > j) return n;
		if (cons(i)) break;
		i++;
		}
		i++;
		n++;
		while(true)
		{  if (i > j) return n;
		if (! cons(i)) break;
		i++;
		}
		i++;
		}
		}

		/* vowelinstem() is true <=> 0,...j contains a vowel */

		private final boolean vowelinstem()
		{  int i; for (i = 0; i <= j; i++) if (! cons(i)) return true;
		return false;
		}

		/* doublec(j) is true <=> j,(j-1) contain a double consonant. */

		private final boolean doublec(int j)
		{  if (j < 1) return false;
		if (b[j] != b[j-1]) return false;
		return cons(j);
		}

		/* cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel - consonant
	      and also if the second c is not w,x or y. this is used when trying to
	      restore an e at the end of a short word. e.g.

	         cav(e), lov(e), hop(e), crim(e), but
	         snow, box, tray.

		 */

		private final boolean cvc(int i)
		{  if (i < 2 || !cons(i) || cons(i-1) || !cons(i-2)) return false;
		{  int ch = b[i];
		if (ch == 'w' || ch == 'x' || ch == 'y') return false;
		}
		return true;
		}

		private final boolean ends(String s)
		{  int l = s.length();
		int o = k-l+1;
		if (o < 0) return false;
		for (int i = 0; i < l; i++) if (b[o+i] != s.charAt(i)) return false;
		j = k-l;
		return true;
		}

		/* setto(s) sets (j+1),...k to the characters in the string s, readjusting
	      k. */

		private final void setto(String s)
		{  int l = s.length();
		int o = j+1;
		for (int i = 0; i < l; i++) b[o+i] = s.charAt(i);
		k = j+l;
		}

		/* r(s) is used further down. */

		private final void r(String s) { if (m() > 0) setto(s); }

		/* step1() gets rid of plurals and -ed or -ing. e.g.

	          caresses  ->  caress
	          ponies    ->  poni
	          ties      ->  ti
	          caress    ->  caress
	          cats      ->  cat

	          feed      ->  feed
	          agreed    ->  agree
	          disabled  ->  disable

	          matting   ->  mat
	          mating    ->  mate
	          meeting   ->  meet
	          milling   ->  mill
	          messing   ->  mess

	          meetings  ->  meet

		 */

		private final void step1()
		{  if (b[k] == 's')
		{  if (ends("sses")) k -= 2; else
			if (ends("ies")) setto("i"); else
				if (b[k-1] != 's') k--;
		}
		if (ends("eed")) { if (m() > 0) k--; } else
			if ((ends("ed") || ends("ing")) && vowelinstem())
			{  k = j;
			if (ends("at")) setto("ate"); else
				if (ends("bl")) setto("ble"); else
					if (ends("iz")) setto("ize"); else
						if (doublec(k))
						{  k--;
						{  int ch = b[k];
						if (ch == 'l' || ch == 's' || ch == 'z') k++;
						}
						}
						else if (m() == 1 && cvc(k)) setto("e");
			}
		}

		/* step2() turns terminal y to i when there is another vowel in the stem. */

		private final void step2() { if (ends("y") && vowelinstem()) b[k] = 'i'; }

		/* step3() maps double suffices to single ones. so -ization ( = -ize plus
	      -ation) maps to -ize etc. note that the string before the suffix must give
	      m() > 0. */

		private final void step3() { if (k == 0) return; /* For Bug 1 */ switch (b[k-1])
		{
		case 'a': if (ends("ational")) { r("ate"); break; }
		if (ends("tional")) { r("tion"); break; }
		break;
		case 'c': if (ends("enci")) { r("ence"); break; }
		if (ends("anci")) { r("ance"); break; }
		break;
		case 'e': if (ends("izer")) { r("ize"); break; }
		break;
		case 'l': if (ends("bli")) { r("ble"); break; }
		if (ends("alli")) { r("al"); break; }
		if (ends("entli")) { r("ent"); break; }
		if (ends("eli")) { r("e"); break; }
		if (ends("ousli")) { r("ous"); break; }
		break;
		case 'o': if (ends("ization")) { r("ize"); break; }
		if (ends("ation")) { r("ate"); break; }
		if (ends("ator")) { r("ate"); break; }
		break;
		case 's': if (ends("alism")) { r("al"); break; }
		if (ends("iveness")) { r("ive"); break; }
		if (ends("fulness")) { r("ful"); break; }
		if (ends("ousness")) { r("ous"); break; }
		break;
		case 't': if (ends("aliti")) { r("al"); break; }
		if (ends("iviti")) { r("ive"); break; }
		if (ends("biliti")) { r("ble"); break; }
		break;
		case 'g': if (ends("logi")) { r("log"); break; }
		} }

		/* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */

		private final void step4() { switch (b[k])
			{
			case 'e': if (ends("icate")) { r("ic"); break; }
			if (ends("ative")) { r(""); break; }
			if (ends("alize")) { r("al"); break; }
			break;
			case 'i': if (ends("iciti")) { r("ic"); break; }
			break;
			case 'l': if (ends("ical")) { r("ic"); break; }
			if (ends("ful")) { r(""); break; }
			break;
			case 's': if (ends("ness")) { r(""); break; }
			break;
			} }

		/* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */

		private final void step5()
		{   if (k == 0) return; /* for Bug 1 */ switch (b[k-1])
		{  case 'a': if (ends("al")) break; return;
		case 'c': if (ends("ance")) break;
		if (ends("ence")) break; return;
		case 'e': if (ends("er")) break; return;
		case 'i': if (ends("ic")) break; return;
		case 'l': if (ends("able")) break;
		if (ends("ible")) break; return;
		case 'n': if (ends("ant")) break;
		if (ends("ement")) break;
		if (ends("ment")) break;
		/* element etc. not stripped before the m */
		if (ends("ent")) break; return;
		case 'o': if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't')) break;
		/* j >= 0 fixes Bug 2 */
		if (ends("ou")) break; return;
		/* takes care of -ous */
		case 's': if (ends("ism")) break; return;
		case 't': if (ends("ate")) break;
		if (ends("iti")) break; return;
		case 'u': if (ends("ous")) break; return;
		case 'v': if (ends("ive")) break; return;
		case 'z': if (ends("ize")) break; return;
		default: return;
		}
		if (m() > 1) k = j;
		}

		/* step6() removes a final -e if m() > 1. */

		private final void step6()
		{  j = k;
		if (b[k] == 'e')
		{  int a = m();
		if (a > 1 || a == 1 && !cvc(k-1)) k--;
		}
		if (b[k] == 'l' && doublec(k) && m() > 1) k--;
		}

		/** Stem the word placed into the Stemmer buffer through calls to add().
		 * Returns true if the stemming process resulted in a word different
		 * from the input.  You can retrieve the result with
		 * getResultLength()/getResultBuffer() or toString().
		 */
		public void stem()
		{  k = i - 1;
		if (k > 1) { step1(); step2(); step3(); step4(); step5(); step6(); }
		i_end = k+1; i = 0;
		}
	}
}
